Performing a Basic Match-Merge

Merging SAS Data Sets

Performing a Basic Match-Merge

After all input data sets are sorted or indexed by the value of a BY variable, you can merge the data sets using a DATA step that contains MERGE and BY statements.

General form, basic DATA step for match-merging:
DATA output-SAS-data-set;
MERGE SAS-data-set-1 SAS-data-set-2;
BY variable(s);
RUN;

where

output-SAS-data-set names the data set to be created
SAS-data-set-1 and SAS-data-set-2 are input data sets
variable(s) in the BY statement specifies the variable(s) whose values are used to match observations.

You can specify any number of input data sets in the MERGE statement.

For example, suppose you have sorted the data sets Clinic.Demog and Clinic.Visit as follows.

     proc sort data=clinic.demog;
        by id;
     run;

Obs ID Age Sex Date

1 A001 21 m 05/22/75

2 A002 32 m 06/15/63

3 A003 24 f 08/17/72

4 A004 . 03/27/69

5 A005 44 f 02/24/52

6 A007 39 m 11/11/57


     proc sort data=clinic.visit;
        by id;
     run;

Obs	ID	Visit	SysBP	DiasBP	Weight	Date
1	A001	1	140	85	195	11/05/98
2	A001	2	138	90	198	10/13/98
3	A001	3	145	95	200	07/04/98
4	A002	1	121	75	168	04/14/98
5	A003	1	118	68	125	08/12/98
6	A003	2	112	65	123	08/21/98
7	A004	1	143	86	204	03/30/98
8	A005	1	132	76	174	02/27/98
9	A005	2	132	78	175	07/11/98
10	A005	3	134	78	176	04/16/98
11	A008	1	126	80	182	05/22/98

You can then submit this DATA step to create Clinic.Combined by merging Clinic.Demog and Clinic.Visit according to values of the variable ID.

     data clinic.combined;
        merge clinic.demog clinic.visit;
        by id;
     run;
     proc print data=clinic.combined;
     run;

Notice that all observations, including unmatched observations and observations with missing data, are written to the output data set.

Obs ID Age Sex Date Visit SysBP DiasBP Weight

1 A001 21 m 11/05/98 1 140 85 195

2 A001 21 m 10/13/98 2 138 90 198

3 A001 21 m 07/04/98 3 145 95 200

4 A002 32 m 04/14/98 1 121 75 168

5 A003 24 f 08/12/98 1 118 68 125

6 A003 24 f 08/21/98 2 112 65 123

7 A004 . 03/30/98 1 143 86 204

8 A005 44 f 02/27/98 1 132 76 174

9 A005 44 f 07/11/98 2 132 78 175

10 A005 44 f 04/16/98 3 134 78 176

11 A007 39 m 11/11/57 . . .

12 A008 . 05/22/98 1 126 80 182

Obs	ID	Age	Sex	Date	Visit	SysBP	DiasBP	Weight
1	A001	21	m	11/05/98	1	140	85	195
2	A001	21	m	10/13/98	2	138	90	198
3	A001	21	m	07/04/98	3	145	95	200
4	A002	32	m	04/14/98	1	121	75	168
5	A003	24	f	08/12/98	1	118	68	125
6	A003	24	f	08/21/98	2	112	65	123
7	A004	.		03/30/98	1	143	86	204
8	A005	44	f	02/27/98	1	132	76	174
9	A005	44	f	07/11/98	2	132	78	175
10	A005	44	f	04/16/98	3	134	78	176
11	A007	39	m	11/11/57		.	.	.
12	A008	.		05/22/98	1	126	80	182